Method and Apparatus for Calibrating Voltage Transformer Serial Addition

Abstract

A series summation-calibrating device based on a semi-insulating voltage transformer includes a symmetrical high voltage test power supply, a three-port serial voltage transformer, a semi-insulating voltage transformer and an error measuring apparatus. The present invention is characterized by: a complete set of equipment for measuring the traceability of power frequency voltage ratio can be manufactured; calibrating the line according to the serial addition based on the semi-insulating voltage transformer; measuring the relative error between the three-port serial voltage transformer and the semi-insulating voltage transformer; and mathematically processing the measuring result to obtain the voltage coefficient curve of the semi-insulating voltage transformer error. The method is easy to operate without being restricted by voltage level, and can establish, from a low voltage of 10V to a high voltage of 1,000V, a standard power frequency voltage ratio measurement system serving as a measurement standard at the national or provincial/ministerial level.

What is claimed is: 
     
         1 . A series summation calibrating device for a voltage transformer, comprising a symmetry high-voltage test power supply, a series voltage transformer having three-ports, a semi-insulating voltage transformer, an error measuring device, and a plurality of connecting wires, wherein an output of said symmetry high-voltage test power supply is respectively communicated with an input of said series voltage transformer having three-ports and an input of said semi-insulating voltage transformer, wherein said symmetry high-voltage test power supply does not only output an independent voltage, but also output symmetry voltages, which is used for generating and changing a high-voltage power supply for calibrating, wherein output signals from said series voltage transformer having three-ports and said semi-insulating voltage transformer are received by said error measuring device, wherein said error measuring device is used for measuring a voltage error of a voltage U 2  of an output of said series voltage transformer having three-ports, referencing a voltage U 3  of an output of said semi-insulating voltage transformer. 
     
     
         2 . The series summation calibrating device, as recited in  claim 1 , wherein said series voltage transformer having three-ports comprises an upstream structure and a downstream structure, wherein a high-voltage side of each of the upstream structure and the downstream structure is connected with a corresponding low-voltage side of each of the upstream structure and the downstream structure in series, and a secondary circuit of the upstream structure is configured with a high-voltage isolating unit, wherein an input port of the upstream structure and an input port of the downstream structure can be independently and respectively applied on a voltage, or they are simultaneously applied on a voltage. 
     
     
         3 . A series summation calibrating method for a voltage transformer, comprising the steps of:
 (a) applying a half voltage  0  on a port of an upstream structure of the series voltage transformer having three-ports and applying a half voltage U/2 on a port of an downstream structure of the series voltage transformer having three-ports via the symmetry high-voltage test power supply, wherein the error measurement is ε1;   (b) applying a half voltage U/2 on a port of an upstream structure of the series voltage transformer having three-ports and applying a half voltage  0  on a port of an downstream structure of the series voltage transformer having three-ports via the symmetry high-voltage test power supply, wherein the error measurement is ε2; and   (c) applying a half voltage U/2 on a port of an upstream structure of the series voltage transformer having three-ports and applying a half voltage U/2 on a port of an downstream structure of the series voltage transformer having three-ports via the symmetry high-voltage test power supply, wherein the error measurement is ε3;   wherein letting respectively an error measurements of said semi-insulating voltage transformer under said conditions of a half voltage U/2 and a total voltage U be γ and γ′, and figuring error change values of said semi-insulating voltage transformer under said conditions of a half voltage U/2 and a total voltage U out by a formula of   
       
         
           
             
               
                 
                   
                     γ 
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                   - 
                   γ 
                 
                 = 
                 
                   
                     
                       
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                         2 
                       
                       + 
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                     2 
                   
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                     3 
                   
                 
               
               , 
             
           
         
       
       and then obtaining synthetically a voltage coefficient curve of said semi-insulating voltage transformer by an interpolation method.